1. Field of the Invention:
This invention relates to a method for reducing or eliminating corneal opacity due to edema and more particularly to a method for treating corneal edema by topical application of solutions of diatrizoate salts.
2. Brief Description of the Prior Art:
The cornea of the human eye in its normal condition is a thin, curved transparent window that covers the front portion of the globe, provides the major part of the refractive power of the eye and transmits light to the interior of the eye where it is focused on the retina by the crystalline lens. The major structural element of the cornea, occupying most of its thickness, is the stroma, which is a differentiated connective tissue. As such it is composed of collagen fibrils arranged in a regular order at a spacing less than a wavelength of light within a ground mass of glycosaminoclycan (GAG) which serves to support the fibrils and protect them. The stroma typically contains about 75% to 80% by weight of water. This water content is critical for maintaining the transparency of the cornea; if the proportion of water exceeds the normal amount, the cornea becomes edematous and takes on a whitish cloudy appearance, which may become so dense as to obscure vision entirely. Maintaining the proper degree of hydration of the corneal stroma is facilitated by the two layers of cells which bound the stromal layer.
The anterior surface of the cornea is covered with a layer of epithelial cells, which among other functions, prevent the diffusion of water from the tear fluid into the stroma. However, the corneal epithelium itself may under some circumstances become edematous and cloudy.
The posterior surface of the cornea is covered with an endothelial cell layer that both serves as barrier to diffusion of water from the aqueous humor of the anterior chamber into the stroma and actively pumps water out of the stroma to maintain the proper degree of hydration. If either the epithelial layer or the endothelial layer is disrupted or injured so that it cannot perform its function of excluding or removing water from the stroma, a corneal opacity, either localized or general, may develop.
While corneal opacities due to problems in the epithelial or endothelial layer tend to resolve themselves over time as the layers heal, it is sometimes necessary in ophthalmological practice to clear a corneal opacity rapidly. For example, it may be necessary to restore vision while the healing of the relevant layers is occurring. A common occasion in which it is desirable to remove the corneal opacity quickly is when a person having such a condition presents for treatment. Under these conditions, the corneal opacity prevents the ophthalmologist from examining the interior structures of the eye for purposes of diagnosis.
It is known to treat edema of the corneal epithelium or stroma by topical application of glycerin. This method is suitable for treatment of epithelial edema and stromal edema due to breaks in the epithelium, e.g., those caused by abrasion. Perfusion of the anterior chamber with a hypertonic solution of glucose has been shown to reduce the hydration of the corneal stroma.
However, a need has continued to exist for additional methods of rapidly clearing corneal opacities due to excessive hydration of the cornea.